PySIM write SMSC

Hey Baseband, I've got a stock of SIMs I bought and programmed already, but I unfortunately (and stupidly) forgot to set the SMSC. This is causing me heaps of issues, as each phone now has to have the SMSC set manually. I was hoping to hack up a quick script which just inserts the SMSC onto the SIM without needing to regenerate the ki or IMSI. Lining those up with my database is rife with hazard. Looking at the pySim-prog, it looks like this probably isn't possible; all of the data seems to get bundled together and so changing the SMSC length will cause other data to be corrupted. Is that right? I just wanted to see what ya'll think would be the best way for me to remedy my particular stupidity. Thanks!